Routing is a behavior that delivers information from a source to a destination. A routing behavior usually includes two basic actions: determining a best route and delivering data. Metric is a measurement used by a routing algorithm to determine the best route to the destination, such as bandwidth or path cost. To help select the route, the routing algorithm initializes and maintains a routing table that includes routing information, where routing information varies with the routing algorithm in use. When the router receives a packet, the router checks the destination address and attempts to connect the address with its next hop. A routing table includes multiple types of information including distance information, hop count information and information of the next hop address. Metrics vary with the routing algorithm in use. The routing table compares the metrics to determine the best route. A router communicates with other routers to maintain its routing table by exchanging routing information. Routing update information usually concerns all or part of the routing tables. The router builds a network topology map by analyzing routing update information from other routers. Another example of information exchange between routers is the exchange of link state advertisements. A router notifies its link-state information to other routers by sending an advertisement. The link state information is used for building a complete topology map so that the router can determine the best route.
Multi-homing is a technique to increase the reliability of the Internet connection, which means that a user connects to the Internet by more than one link. In fact, Traffic Engineering (TE) is a set of tools and methods, which can get the best service from given infrastructure no matter whether a network device or a transport line works normally or fails. This requires optimization of the used resources. With the wide deployment of multi-homing and TE systems, Internet routes increase rapidly. As a result, on the one hand, because larger capacity chips are needed to store larger routing tables, the cost of routers is growing; on the other hand, route convergence becomes slower, which hinders system response and affects efficiency of the entire system.
Because a routing table in the prior art includes specific routes to target subnets, when Internet routes increase rapidly, corresponding routing information must be added in routers in the Transit Network (TN) and the Edge Network (EN), so that the size of a routing table also increases rapidly. As a result, the cost for devices to store routing tables rises and route convergence becomes slower. The efficiency of the entire system is therefore low.